[android_webview] Fix use after free in intercepted requests.

android_webview/browser/input_stream.h

Index: android_webview/browser/input_stream.h
diff --git a/android_webview/browser/input_stream.h b/android_webview/browser/input_stream.h
index c0a3ab205af7d43e919e116362e09439da1641e8..8ef476581f517f6b0521de93826b216eda8b9596 100644
--- a/android_webview/browser/input_stream.h
+++ b/android_webview/browser/input_stream.h
@@ -14,6 +14,9 @@ class IOBuffer;
 namespace android_webview {
 
 // Abstract wrapper used to access the InputStream Java class.
+// This class is safe to pass around between threads (the destructor,
+// constructor and methods can be called on different threads) but calling
+// methods concurrently might have undefined results.
 class InputStream {
  public:
   virtual ~InputStream() {}